Here is a site which takes a song in a minor key (usually kind of melancholy) and convert it to major key (cheerful, upbeat http://vimeo.com/majorscaledtv

The interesting part is how they did it. With the popularity of the game "Guitar Hero" a great number of songs have been released in multitrack - giving you access to the vocal tracks, the drum track, the guitar tracks, etc. Then there are a number of software packages which allow remixing and changing entire sounds. Here is an article on how (they think) they did it.http://evolver.fm/2013/01/24/how-major-key-version-of-r-e-m-s-losing-my-religion-was-made/